Improvement of Photovoltaic Performance of Octahexylphthalocyanine-Based Bulk-Heterojunction Solar Cells Using Various Fullerene Derivatives

Abstract

The improvement of the photovoltaic performance of 1,4,8,11,15,18,22,25-octahexyl-phthalocyanine (C6PcH₂)-based bulk-heterojunction solar cells using various fullerene derivatives was studied. By using asymmetric fullerene derivatives, the external quantum efficiency of the solar cells at around 500 nm was improved from 8% to 24%, and the short-circuit current density increased from 8.09 to 10.17 mA・cm^-2. An open-circuit voltage of 0.96 V was achieved by a using fullerene derivative with a high lowest unoccupied molecular orbital. The photovoltaic properties were also discussed, taking into consideration the effects of adding the fullerene on the crystallization of C6PcH₂ molecules in the hexagonal structure and the optical properties.